Apple testing 6-inch iPhone concepts, of course

Apple has so far released 3.5-inche iPhones from 2007 to 2011, and a 4-inch iPhone in 2012. However, to get to those very specific sizes, Apple likely prototyped everything at quarter-inch intervals in-between. That's why they have Jony Ive, the design group, and all that fancy prototyping equipment in the labs. Which screen size(s) eventually get released and when is a far more interesting question, and difficult one. Here's what Ian Sherr, Eva Dou, and Lorraine Luk for the Wall Street Journal:

The electronics giant has begun evaluating a plan to offer iPhones with screens ranging from 4.8 inches to as high as 6 inches, people familiar with the matter say. That would be a sizable leap from the 4-inch screen of the iPhone 5 released last year, and, at the upper end, would be one of the largest on the market.

Beyond the prototyping process, however, a larger screen the idea a larger screen iPhone moving from prototype into product has been getting more attention over the last year or so, and could be getting much more attention next year. The math works out for a 5 inch iPhone. From 4.3- to 5-inches in probably the sweet spot. 6-inches seems a little on the big side, but could make sense for emerging markets where phones are primary computing devices.

Sure, bigger screens aren't as easy to use one-handed, but casing size can be reduced around the screen, like with the Moto X or come up with software solutions like the gesture navigation in on the BlackBerry Z10.

There's not as much pressure in U.S. markets quite yet, which is why Apple is probably going with a less expensive iPhone 5C instead of a larger screen iPhone right now, but the time will likely come for that soon enough. Perhaps even next.

Once you have the iPhone and its market, increasing that market by annexing adjoining segments just makes sense. Less expensive this year, for first time buyers who are more price sensitive, larger screen next year for people for whom the computing aspect is more important than the phone aspect, and so on.